Binge eating among the overweight is a serious clinical problem. Among overweight individuals seeking treatment, 30% meet the proposed criteria for binge eating disorder (BED). The incidence of binge eating increases with increasing levels of adiposity and is associated with a history of marked weight fluctuations. BED patients experience more eating disorder pathology (e.g., distorted attitudes toward eating, shape, and weight) and general psychopathology (e.g., depression, anxiety) than the non-binge eating obese. To date, most binge eaters have been tread in traditional weight loss programs which do not appear to lead to long-term improvements in binge eating or reductions in-associated eating disorder pathology. Moreover, BED patients may be more likely to drop out of treatment and regain weight faster than non-binge eaters. Given these findings and evidence of similarities between overweight binge eaters and normal-weight patients with bulimia nervosa (BN), we conceptualize binge eating as a serious problem requiring intensive psychological treatment. Few studies have systematically investigated psychological treatments for overweight binge eaters. Recently two treatments adapted from BN to BED that specifically treat the eating disorder have shown promise: group Cognitive-Behavior Therapy (CBT) and group Interpersonal Psychotherapy (IPT). CBT and IPT are derived from different theoretical traditions, assume different etiology for binge eating, and involve entirely different intervention strategies. The work proposed here is designed to compare these treatments and to identify the mechanisms by which they achieve their effects. Over a four year period, 162 overweight men and women who meet criteria for Binge Eating Disorder will be randomly assigned to either group CBT or group IPT. In total, there will be 18 groups with 9 per treatment condition. Treatment will be administered in small groups that meet for 20 weekly sessions. The assessment points will be at: I) baseline; 2) midtreatment; 3) posttreatment; and 4) at 4, 8, and 12 month follow-up assessments. This study will compare two commonly used theories and offer data relevant to the etiology and treatment of binge eating. Additional objectives are to identify the mechanisms by which they achieve their effects and to identify predictors of treatment outcome. Identifying mechanisms will ultimately lead to more efficient and effective treatments whereas identifying predictors of treatment outcome will provide information about the matching of binge eaters to the two treatments: CBT or IPT.